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Direct reduction processes can be divided roughly into two categories: gas-based and coal-based. In both cases, the objective of the process is to remove the oxygen contained in various forms of iron ore (sized ore, concentrates, pellets, mill scale, furnace dust, etc.) in order to convert the ore to metallic iron, without melting it (below 1,200 °C (2,190 °F)).
In the iron and steel industry, direct reduction is a set of processes for obtaining iron from iron ore, by reducing iron oxides without melting the metal. The resulting product is pre-reduced iron ore. Historically, direct reduction was used to obtain a mix of iron and slag called a bloom in a bloomery.
Direct reduction is the fraction of iron oxide reduction that occurs in a blast furnace due to the presence of coke carbon, while the remainder - indirect reduction - consists mainly of carbon monoxide from coke combustion. It should also be noted that many non-ferrous oxides are reduced by this type of reaction in a blast furnace.
The HIsarna ironmaking process is a direct reduced iron process for iron making in which iron ore is processed almost directly into liquid iron ().The process combines two process units, the Cyclone Converter Furnace (CCF) for ore melting and pre-reduction and a Smelting Reduction Vessel (SRV) where the final reduction stage to liquid iron takes place.
The reduced iron agglomerates into 3 to 8 mm metal nodules called Luppen. If the infusibility of the gangue is high, the temperature must be increased, up to 1,400 °C for a basic charge. [22] It is crucial to control the gangue's hot viscosity. [9] Among rotary drum direct reduction processes, it stands out for using high temperatures.
Depending on the temperature in the different parts of the furnace (warmest at the bottom) the iron is reduced in several steps. At the top, where the temperature usually is in the range between 200 °C and 700 °C, the iron oxide is partially reduced to iron(II,III) oxide, Fe 3 O 4. 3 Fe 2 O 3(s) + CO (g) → 2 Fe 3 O 4(s) + CO 2(g) [9]
Iron ore pellets produced by LKAB, from ore mined in northern Sweden. Pellets are a processed form of iron ore utilized in the steel industry, specifically designed for direct application in blast furnaces or direct reduction plants. These pellets are spherical in shape, with diameters ranging from 8 to 18 millimeters.
The Flodin process is a direct reduction process for manufacturing modern iron and steel, developed by Gustaf Henning Flodin from Sweden and patented in 1924. It has been used in Norway, Sweden, and the United States.